A wire-cutting electroerosion machine, which is also called a traveling-wire electroerosion machine, commonly makes use of a thin elongated electrode tool in the form of a wire, filament or tape (herein generally called "wire-electrode tool") composed of, say, tungsten, brass or copper and having a thickness generally from 0.05 to 0.5 mm. The machine commonly includes drive means, e.g. capstan and pinch rollers, for axially moving the wire-electrode tool along a continuous path extending from a supply side, e.g. a storage reel, to a collection side, e.g. a takeup reel, through the region of a workpiece. Included also in the machine is an electroerosion power supply for feeding a machining current between the moving wire-electrode tool and the workpiece across a small machining gap flooded with a liquid machining medium which may be either a liquid electrolyte or a liquid dielectric such as distilled water or kerosene. The power supply is typically or preferably adapted to furnish between the electrode tool and the workpiece a succession of electrical pulses to electrically energize the liquid-filled machining gap. When the gap is energized, stock of the workpiece is removed electrophysically and/or electrochemically, depending on the type of the liquid machining medium, to "machine" the workpiece. In a certain sophisticated electroerosive wire-cutting machine, abrasive media are included in the machining liquid to mechanically assist the stock removal or promote the stability of the electroerosion action, thereby enhancing the efficiency of the stock-removal process. As stock removal proceeds, the workpiece is displaced relative to the axially moving electrode tool and generally transverse to the axis thereof along a prescribed path, conveniently under the commands of a numerical control (NC) unit, to form a desired cut in the workpiece with due precision.
For conducting the machining current to the moving wire-electrode tool, a brush is customarily used and connected to one output terminal of the power supply whose other output terminal is connected to the workpiece. The brush in the form of a block is customarily disposed intermediate adjacent guide members and positioned to bear against the wire-electrode tool moving from one guide member to the other. To ensure satisfactory bearing electrical contact with the moving wire-electrode tool, the brush must be urged under considerable pressure against the tool which is thin and stretched tightly while moving. Thus, the brush wears away, forming a groove therein with its width corresponding to the thickness of the wire-electrode tool. The depth of the groove increases rapidly so that the brush becomes useless and its replacement by a new brush becomes necessary in a relatively short period of time. The time in which the brush becomes useless is further reduced when the machining liquid has abrasive media suspended therein. It can be seen, therefore, that the conventional tool-conducting arrangement gives rise to practical problems and have considerably limited the efficiency of wire-cutting electroerosion machines.